Luminaires which are to be used for outdoor lighting are quite frequently used in situations which require a light distribution pattern of a specific shape and which also have rather severe restrictions on the mounting supports available at reasonable cost. These requirements and limitations are not only inconsistent in some circumstances but are often not predictable until the luminaire is taken to the point of installation and use. For most luminaires, the lighting pattern is a relatively unchangeable function of the available mounting or, alternatively, special arrangements must be made at extra cost.
For example, if an outdoor sign is to be illuminated by a number of units mounted on the sign support, the desired pattern of light depends upon the relationship of the sign shape and the support position. If the sign aspect is relatively tall and narrow, a vertically spread pattern is needed. Alternatively, if the width is greater, a horizontal pattern is desired, but the available support for the luminaire may be the same in both cases. Obviously, if one form of luminaire is available, then one of the signs will not be properly lighted.
Similar problems arise when mounting a plurality of units to illuminate an area such as a building exterior, playing field or parking region. While special purpose luminaires for each of these uses exist, it is not desirable to have to maintain an inventory of a large number of different kinds of units.